Many endoprosthesis, such as, for example, stent-grafts, are constructed to reinforce, replace, bridge, or otherwise treat a part of a blood vessel. An endoprosthesis may guide blood flow through a lumen defined by a generally tubular interior of such a vessel. Other tubular endoprostheses are designed for use in other body regions, for example, the esophagus, ureters, gastrointestinal tract and various ducts. In many cases, endoprostheses are constrained within a covering member or sheath and delivered to the body region requiring treatment on the end of an elongate member. When the covering member is removed, as during deployment, the devices are expanded under force or self-expand to assume a larger diameter. After delivery and deployment of the endoprosthesis, the elongate member used to delivery and deploy the endoprosthesis is retracted into a tubular outer shaft and removed from the body. In some instances, it may be difficult to properly align the elongate member and endoprosthesis with the outer shaft, causing difficulties in retraction. Thus, improved endoprosthesis delivery systems are desirable.